Lead shot conventionally is employed in shotguns. The density of lead provides a ballistic efficiency which has not been matched by any other readily available material, such as steel. Unfortunately, lead presents a serious toxicity problem to waterfowl. Spent shot lying on the bottom of shallow lakes and marshes within reach of feeding ducks and geese is sometimes ingested along with similar sized gravel and taken into the gizzard of the bird. After being broken down in the gizzard, the lead is absorbed into the bird's system, often in lethal doses. Studies have shown that the number of waterfowl which die from lead poisoning have been significant, one 1959 study indicating two to three million deaths in North America. Steps have been taken in some areas of the United States to ban the use of lead shot in favor of steel shot for hunting wildfowl.
Attempts have been made to alleviate this problem, without any significant success. One approach which has been taken is to coat shot in an attempt to isolate the lead from the wildfowl digestive system, but both metallic and non-metallic coatings have been unsuccessful to date. Tin, copper and magnesium coatings were quickly ground off by the abrasive action of the bird's gizzard. Nylon and many similar plastics have a melting point so near to that of lead that coating is impractical. Successfully applied plastic coatings have been found to resist the abrasive action of the gizzard no better than the above-noted metals and, indeed, in the instance of one epoxy resin, hastened the death of ducks. Other forms of coating include nickel coatings as applied to the lead shot. Such nickel coating was applied by electrodeposition techniques to a thickness in the range of 0.001 to 0.003 of an inch. However in tests, inadequate results were realized due primarily to the fact that the nickel coating, as provided by electrodeposition, is of insufficient Rockwell hardness of approximately 35. Hence the nickel coating was ground off in the digestive system of the wildfowl, thereby exposing the lead and causing lead poisoning.
Iron and steel shot are non-toxic but are ballistically inferior to lead and damage shotgun barrels. Steel shot occupies a much greater volume than the same weight of lead shot and fitting a sufficient number of steel shot to provide adequate shot pattern into existing shell cases is a major difficulty. Solid copper shot is ballistically more efficient than iron and does little damage to gun barrels, but is almost as toxic as lead.